How to Flush & Change Antifreeze

[BigEasy]

Planning to flush & change antifreeze in my Yanmar 3YM30. (have owned the boat for 2 1/2 years). Would appreciate anyone who has done this to give me an idea of the procedure that you used. Service manual is no help.

PO had red coolant as evidenced by residual in bilge. The system now has green antifreeze. According to Yanmar, the recommended coolant is 50/50 concentration of Havoline Extended Life (red stuff). I understand that I need to thoroughly flush the system when converting from one coolant to another; therefore, I would like to completely empty the system and flush.

Any info regarding emptying system including location of drains, vacuuming vs pressure flushing vs gravity flushing of block/heat exchanger/water heater would be helpful. Also how to flush the system and if use of chemical flush is necessary, and how to refill without air lock. Many thanks, David

 

[Johnb]

14 years ago when I did not know exactly what was in there I just did a double change. I suspect you could use pure water in between. Since then just change at regular intervals.

All I ever do is drain using the engine and water tank drain points. I figure if you service a little more often than required it is O.K. to have a few drops remaining.

My overflow tank works perfectly and it seems as though air bubbles go out that way. Sometimes after the first running following a change the overflow tank gets a little low when cooling and I add to the midway mark. After that I have never added coolant between changes.

I have used a coolant and distilled water mix and it seems to have paid off. All the problems I have ever had have been on the raw water side. I did get a new Yanmar water tank. Engine is a 3QM30.

 

[BigEasy]

John,
Where exactly are the coolant drains located on the engine?

 

[DougM]

Out of curiosity, how frequently do any of you drain and flush your closed cooling systems? I would think that the havoline (orange) is formulated to last far longer than the old green antifreeze.

Second question: where do you dispose of the old coolant? Some places won't accept it because they cannot get rid of it safely.

 

[BigEasy]

Doug,
Yanmar recommends replacement of coolant every two years if extended life coolant is used (Havoline extended life). I have seen where other posters take the old coolant to an oil change garage for disposal. Guess that you can offer them a few dollars to dispose of it for you.

 

[Ralph Johnstone]

Frequency of Coolant Changes

Out of curiosity, how frequently do any of you drain and flush your closed cooling systems?

I find it easiest to change the coolant every two years with any well known (same colour) antifreeze such as Prestone. I choose two years due to having longs hoses leading to the hot water heater. This way I don't have to blow them out. Extended antifreeze is for those who don't want to change the coolant regularly.

Using distilled water ensures the antifreeze coming out is just as clear as the new stuff going in.

 

[seadaddler]

coolant

I have a 07 H-36 with 3YM30 and have the same orange coolant
since new and it still looks pretty good and recently added a temp gauge
it the temp 180 is pretty steady and the engine runs very good so I guess
I think why fix what"s not broke and even took the front off the heat exchanger
and was impressed how good everything looked so good.
I guess I will change and flush one of these days.
Nick

 

[DougM]

Doug,
Yanmar recommends replacement of coolant every two years if extended life coolant is used (Havoline extended life). I have seen where other posters take the old coolant to an oil change garage for disposal. Guess that you can offer them a few dollars to dispose of it for you.

It's certainly easy enough to change antifreeze, and it's cheap insurance really. Over simplified,... Just need to pull a drain plug out of the block and out of the inter cooler. Seems like a few folks forget about that length of coolant line that runs to and from the water heater if they have one.

Yanmar recommends two years, yet auto manufacturers will recommend changing at 100K miles with the orange antifreeze. It doesn't seem to equate, particularly when boats in the North only get used around four months annually.the coolant just sits in a closed container so to speak for the balance of the year..

Then there is that select group of owners that may not realize that their engines even contain antifreeze, let alone think about draining and flushing.

 

[Bob 04 H260]

I have a Yanmar 3GM30F. I drained it well, removed the thermostat and the mixing elbow hose. I then used a garden hose to reverse flush both cooling circuits.
Drained the water out. Opened the front of the heat exchanger to check for any goodies.
I blew the flush water out of the hot water heat exchanger with the dinghy air pump.
I refilled with Delo long life coolant as recommended by my Yanmar dealer, it comes premixed.
I replaced the mixing elbow, and all coolant and raw water hoses when the boat turned 10, they appeared to be ok. I have them stored away as emergency spare parts.
The place that sells you fresh coolant should be prepared to take back the used stuff.
Bob

 

[Scott B]

John,
Where exactly are the coolant drains located on the engine?

Did you get the Operators Manual with the boat?

There's one on the hose to the lower end of the heat exchanger and one on the block.

 

[BigEasy]

Scott,
Thanks for the diagram. Appears that there are only two drains for the coolant; one on the hose leading to the heat exchanger and one on the Stbd side of the engine block. I I will try to drain the coolant first and then use Bob's method of removing the thermostat and flushing with a garden hose to pressure flush any gunk out of the system.
Thanks again.